Method of, and apparatus for, propelling railway vehicles



Sept. 15, 1964 D. E. BICK ETAL 3,148,633

METHOD OF, AND APPARATUS FOR. PRDPELLING RAILWAY VEHICLES Filed April V22, 1963 7 INVENTOR$ ATTORNEY.

United States Patent 3,146,633 METHOD OF, AND APPTUS FOR, PRO- PELHNG RAELWAY VEHICLES David E. Rick and Colin R. Little, Cheltenham, England, assignors to Dowty Hydraulic Units Limited, Ashchurch, England, a British company Filed Apr. 22, 1963, Ser. No. 274,411 (Ilaiins. (Cl. 104-162) This invention relates to a method of, and apparatus for, propelling vehicles along a railway track.

The method according to the invention employs a number of fluid pressure operated devices spaced at intervals along a rail in positions in which they are successively engaged by the periphery of a vehicle wheel rolling along the rail, in which the method includes the steps of applying fluid pressure to extend the devices successively in rising engagement with the periphery of the wheel as the wheels point of rolling contact with the rail moves away from each device.

More specifically, the method according to the invention consists in venting to low pressure, fluid which is expelled by contraction of each device caused by a vehicle wheel, and then applying high fluid pressure to the device during subsequent extension against the vehicle wheel, these operations being repeated at each successive device as the wheel rolls over it.

A device for use in carrying out the method comprises a fluid pressure operated unit having piston and cylinder members of which one member is fixed and the other member is adapted for inward and then outward move ment relative to the fixed member by the action of a vehicle wheel rolling along the rail; a volume of liquid is enclosed between the piston and cylinder members, and valve means together with automatic operating means therefor are arranged to connect the volume of liquid with a low pressure exhaust during relative inward movement of the piston and cylinder members, and with a high pressure source during outward movement of piston and cylinder members.

The valve means may be operated mechanically in response to the direction of relative movement of the piston and cylinder members, or it may be operated hydraulically in response to the direction of liquid flow leaving or entering the volume of liquid.

The invention is illustrated in the accompanying drawings, of which FIGURE 1 is a sectional view of one form of vehicle accelerator, and

FIGURE 2 is a diagram of another form of vehicle accelerator.

In the embodiment of FIGURE 1, a cylinder 10 is arranged by means of a bracket 6 fixed thereto and a pair of bolts 7, one of which is seen in the figure, to be attached to a rail 12 in an upright position at one side thereof. A piston 13 slidably mounted in the cylinder 10 has a head 14 fixed to its upper end. A view of the head 14 is drawn in broken outline 14' at right angles to its installed posi tion, in order to show the profile of a curved upper face 8 thereof which is engageable by the flange of a vehicle wheel rolling along the rail 12. The head 14 lies close alongside the rail and it is prevented from turning by a pair of cars 9, also shown in profile at 9', which never rise to the top of the rail, but can slide against one side of the rail 12. The piston 13 enters through a sealing ring assembly 15 in the upper part of the cylinder 10 and its lower part has fixed thereto a downwardly extending central stem 16 which terminates in a flange 17. The flange ice 17 constitutes a valve-operating abutment which is engageable under the flange 18 of a cylindrical slide valve element 19 which is slidable in a counter-bore 21 at the lower end of the cylinder 10. The counter-bore 21 is of larger diameter than the bore 22 of the cylinder in which the piston 13 slides and a step 23 at the meeting of the bores forms an UP limit stop for the slide valve 19. The step 23 also forms an UP limit stop for the piston 13 by virtue of the engagement of the flange 17 under the flange 18. A high pressure screw connector 24 fixed on the side of the cylinder 10 opens through a high pressure port 25 in the cylinder 5 into the counter-bore 21, while a low pressure screw connector 26 fixed on the side of the cylinder 10 opens through a port 27 in the cylinder which lies axially above the port 25. A peripheral groove 28 in the slide valve 19 opens through radial holes 29 into the interior of the slide valve. The screw connectors 24 and 26 are upon installation of the device connected to the high and low pressure pipes of a hydraulic power source.

The lower end of the cylinder 10 is closed by a screw cap 31 which supports a spacer 32 forming a DOWN limit stop for the slide valve 19. A packing ring 33 is recessed into the periphery of the slide valve 19 to provide friction against the counter-bore 21 which holds the slide valve in either of its end positions. In this embodiment, it is necessary that the slide valve 19 shall be moved downwardly when the piston 13 nears the end of its downward movement under the rolling motion of a vehicle wheel flange passing over the head 14, but it is also necessary that engagement of the slide valve 19 with the spacer 32 shall provide no end stop to downward movement of the piston 13. It is accordingly arranged to actuate the slide valve 19 by a coil spring 34 which is located on the stem 16. This spring 34 rests on the flange 18 of the slide valve 19 and it is compressed by the end face 11 of a counter-bore in the piston 13 when the latter nears the end of its downward stroke.

The stem 16 is hollow and has radial holes 35 connecting an annular liquid-containing chamber 36 which is disposed around the stem 16 with a liquid-containing chamber 37 which is disposed within and below the slide valve '19.

In operation, the flange of a vehicle wheel rolling along the rail engages the head 14 to depress it so that the piston 13 slides downwardly in the cylinder 11 The slide valve 19 in its raised position against the step 23 connects the chamber 37 with the low pressure port 27 by way of the recess 28 and holes 29 so that during downward movement of the piston liquid is expelled from the chambers 36 and 37 at low pressure. Towards the end of the downward stroke of the piston 13, the end face 11 presses the spring 34 until the compression overcomes the friction of the slide valve 19 and its packing ring 33 in the counterbore 21, and shifts the slide valve 19 downwardly against the spacer ring 32. The employment of the spring 34 for shifting the slide valve 19 ensures that the latter moves quickly when static friction is overcome and it also makes allowance for any variation in the downward stroke imparted to the piston 13 by reason of variation in the depth of wheel flanges.

The recess 28 in the slide valve 19 now lies opposite the high pressure port 25 so that when the wheels point of contact with the rail 12 passes away from the central axis of the piston 13 and the piston starts to rise, its rising movement is actuated by the supply of high pressure liquid at the connector 24 and port 25, through the holes 29 and into the chambers 37 and 36. Towards the end of the upward stroke, the flange 17 on the stem 16 engages under the flange 18 of the slide valve 19 and lifts it upwardly against the step 23 so that the chambers 37 and 36 are again placed in communication with low pressure at the port 27 in readiness for the next downward stroke of the piston 13 under another wheel of the same or a following vehicle.

In the example described, the reversing valve is operated mechanically by a lost-motion connection between the piston 13 and the valve 19, but this valve reversal can be obtained in another embodiment of the invention, shown in FIGURE 2, using a valve which is responsive to the direction of fluid flow. The liquid space enclosed between a cylinder and a piston 13 is connected by a single pipe 41 to an external valve 42 having axially pressure and return ports 43 and 44 respectively in its cylindrical housing 45. The pipe 41 enters the housing 45 adjacent an upper end wall 46 and the opposite end of the housing 45 is closed by a lower end wall 47. A movable valve element 48 in the form of a hollow piston is slidably mounted in the bore of the housing 45 and it has radial holes 49 adapted to register with the ports 43 and 44 in the upper and lower positions respectively of the valve element 48. The holes 49 are never fully closed between these positions, but have a slight overlap with the ports 43 and 44 in the intermediate position of the element 48 so as to avoid liquid trapping in the valve. An annular valve seat 51 formed within the element 48 is engageable by a mushroom shaped valve 52 under pressure of a spring 53 which is seated against the end wall 47. A second spring 54 seated against the end wall 46 bears against a shoulder 55 on the valve element 48 to maintain the seat 51 normally engaged against the mushroom valve 52, but the spring 54 is not sutficiently strong to overcome the load in the spring 53 and shift the stem of the mushroom valve 52 out of its normal engagement with the end wall 45, nor to depress valve element 48. The valve element 48 has in effect opposite annular sunfaces between the bore of the housing 45 and the diameter of the seat 51, which are responsive to the liquid pressures on opposite sides of the valve seat 51, while the resistance to liquid flow past these pressureresponsive surfaces and across the valve seat is provided by the springs 53 and 54 which hold the valve elements 48 and 52 together.

In operation, when liquid is expelled from the cylinder 10, it enters the valve housing 45 through the pipe 41 and displaces the valve element 48 and mushroom valve 52 downwardly until the lower end of the valve element 48 engages the end wall 47. In this position the holes 49 lie in register with the low pressure port 44, and continued flow of liquid from the cylinder 10 depresses the mushroom valve 52 from the seat 51 against the load of spring 53 so that liquid flows at low pressure into the port 44. When the flow is reversed on the upward stroke of the piston 13, liquid enters the low pressure port 44 and holes 49 to act upwardly on the valve element 48 and mushroom valve 52 so that both move together in closed relationship to bring the holes 49 into register with the higher pressure port 43. The mushroom valve 52 is then disposed in engagement with the end wall 46, stopping its upward movement, and pressure liquid lifts the valve element 48 against the load of the spring 54 to open a fiow path across the seat 51 into the pipe 41. Liquid under pressure thereupon enters the cylinder 10 to efiect upwardly directed power actuation of the piston 13 against the flange of a vehicle wheel. A small bleed hole 56 across the head of the mushroom valve 52 ensures that the valve element 48 cannot be displaced under static pressure in the pipe 41, caused for example by thermal expansion of hydraulic liquid, to a position where the holes 49 overlap the high and low pressure ports 43 and 44 to cause undesirable power loss.

In the embodiment of FIGURE 2 it is possible to control more than one piston and cylinder device by a single valve 42 provided that the devices are spaced apart and limited in number such that only one of the devices controlled by the valve is operative at any one time during the passage of one or a succession of vehicles along the rail. In FIGURE 2 a second cylinder and piston device 10a, 13a is shown connected to the pipe 41. The cylinders 10 and 10:: will be mounted against the rail at a distance apart which ensures that a vehicle wheel will leave the head 14 of the piston 13 before engaging the head 14a of the piston 13a.

In each of the embodiments described the devices may be duplicated for simultaneous action against two wheels mounted on the same axle.

The upward thrust under hydraulic pressure which each device is capable of exerting against a vehicle wheel should be limited to prevent even the most lightly loaded wheel being lifted off the rail. The desired propulsion of a vehicle will accordingly be obtained by providing a succession of piston and cylinder devices along a required length of track. The speed to which a vehicle can be accelerated by a succession of devices may be limited by the flow capacity of the supply pipes and valve ports which causes the available fluid pressure to fall with increasing speed.

In a railway track or system of railway tracks such as a marshalling yard, a track may in different parts have uphill and downhill gradients and parts with no gradient at all. A method of vehicle speed control over a length of track may accordingly emply vehicle propelling devices, as described in the preceding examples, together with retarding devices and/ or devices capable of retarding and accelerating, such as are described in United States patent specification Serial No. 3,040,676.

Thus, devices as described in the preceding examples may be employed to propel a vehicle along an uphill gradient or along the level, while speed-responsive retarders as in the prior patent may be used to retard a vehicle on a downhill gradient where the vehicle would otherwise be liable to accelerate to an undesirable speed, and furthermore, speed-responsive devices capable oi either retarding or accelerating may be employed on gradual downhill gradients or on the level. A vehicle starting at one end of a length of track is thereby enabled to reach the other end within the limits of acceptable speed.

Vehicle propelling devices in accordance with the invention may be used to assist a self-propelled vehicle in starting a train of vehicles drawn thereby or in propelling the train up an incline.

We claim as our invention:

1. A device for propelling a vehicle along a railway track alongside which said device is located, comprising a unit having relatively movable piston and cylinder members which in use enclose a volume of liquid, one of the members being adapted for fixed mounting adjacent a track rail and the other member being adapted for engagement by the periphery of a vehicle wheel moving along the track rail to effect relative inward closing movement of said members, valve means communicating with said volume of liquid and having high and low pressure ports arranged for connection with pressure and return conduits respectively of a hydraulic power source, said valve means being operable to connect said enclosed volume of liquid with the high and low pressure ports alternatively, and valve-operating means responsive to the direction of relative movement of said members, said valveoperating means being operative to connect the valve means to said volume of liquid with the low pressure port during relative inward closing movement of said members, and with the ig pressure port during relative outward opening movement of said members.

2. A device for propelling a vehicle along a railway track comprising a cylinder member adapted for fixed mounting adjacent a track rail, and a piston member mounted slidably in the cylinder member to enclose therewith a space which in use is filled with liquid, the piston member being adapted for engagement by the periphery of a vehicle wheel moving along the track rail to effect its inward movement in the cylinder member, valve means including high and low pressure ports formed in the cylinder member and a valve element movable axially in the cylinder member between end positions in one of which the liquid-filled space is placed in communication with the high pressure port and in the other end of which it is placed in communication with the low pressure port, and valve-operating elements carried by the piston member in such positions as to effect opposite movements of said valve element when the piston member approaches the ends of its inward and outward movements, said valve element thereby connecting the liquid-filled space to the high pressure port towards the end of the pistons inward movement, to effect its outward movement, and connecting to the low pressure port towards the end of the pistons outward movement, whereby it may subsequently move inwardly again.

3. A device according to claim 2, wherein the valve operating elements comprise a spring which is operable compressively against the valve element towards the end of the pistons inward movement, and an abutment which is engageable with the valve element towards the end of the pistons outward movement.

4. A device for propelling a vehicle along a railway track comprising a unit having relatively movable piston and cylinder members together enclosing a space which in use is filled with liquid, one of the members being adapted for fixed mounting adjacent a track rail and the other member being adapted for engagement by the periphery of a vehicle wheel moving along the track rail to efiect relative inward closing movement of said members, valve means communicating with said volume of liquid and having high and low pressure ports arranged for connection with pressure and return conduits respectively of a hydraulic power source, and valve actuating means operatively interposed between the valve ports and the volume of liquid, said valve-actuating means being responsive to the direction of liquid flow leaving and entering said volume of liquid and thereby causing the valve means to connect said volume of liquid with the low pressure port in response to liquid flow from said volume accompanying inward closing movements, and with the high pressure port in response to liquid flow towards said volume, to effect outward opening movement.

5. A device according to claim 4, wherein said valveactuating means is constituted by a movable element of said valve means, said movable element having opposed pressure-responsive surfaces, and including means afi'ording resistance to liquid flow past said pressure-responsive surfaces.

6. A device for propelling a vehicle along a railway track, alongside which the device is located, comprising relatively reciprocable piston and cylinder members together defining an enclosed volume that in use is filled with liquid, one of said members being adapted for fixed mounting adjacent a track rail and the other member being thereby located for engagement by the periphery of a vehicle wheel moving along the track rail, to eflect movement of such other member downwardly relative to the fixed member, to lessen the enclosed volume of liquid, a high pressure port and a low pressure port communicating with said volume of liquid at axially spaced points, a valve member interposed between said ports and the enclosed volume of liquid, and shiftable between an upper limit position which affords communication between the low pressure port and the enclosed volume, and a lower limit position which affords communication between the high pressure port and the enclosed volume, means to retain said valve member yieldably in its upper limit position, and a valve-operating means located in the fluidfilled space, and shiftable downwardly under the influence of downward movement of the movable member, said valve member being also movable to its lower limit position by, and towards the end of, downward movement of the movable member, for communication between the high pressure port and the fluid-filled space, the high pressure acting to restore said valve-operating means to its upper position upon cessation of such downward movement, the valve-operating means and the valve member being interengageable, as the valve-operating means approaches its upper position, to shift the valve member to its upper limit position for communication between the low pressure port and the fluid-filled space.

7. A method of propelling a vehicle along a railway track by means of a fluid-pressure-actuated device such as includes a first member fixed to the track and a second member movable downwardly relative to the first member by a wheel flange rolling over such second member, and upwardly upon passage of the wheel flange, the two members defining a hydraulic jack, which method comprises confining a volume of liquid within a space of variable volume communicating with the jack, establishing a connection between such space and a region of low pressure for expulsion of liquid from the space under the influence of compression of the jack incident to downward movement of the second member, and establishing a connection between such space and a source of high pressure liquid at conclusion of compression of the jack, for increase in the liquid-filled volume within the space and the communicating jack, to urge the movable member upwardly, and so to impel the wheel as it rolls off the second member.

8. A method of propelling a vehicle along a railway track as set forth in claim 7, by means of a plurality of such hydraulic jacks spaced alongside the track, which method comprises establishing a hydraulic connection between the several jacks and a liquid-filled space common to all such jacks, whereby expulsion of fluid from each successive jack to the common liquid-filled space under the influence of a passing wheel connects that space to the low pressure vent, and passage of the wheel sufficiently that the movable member of that jack can rise initiates upward movement of said movable member and connects that space to the high pressure source.

9. A method of propelling a vehicle along a railway track by means of a fluid-pressure-actuated device which includes a member fixed to the track and a member movable vertically with relation thereto and cooperating therewith to define a fluid-filled space, which method comprises connecting such space normally with a source of low fluid pressure, to retain the movable member upraised into the path of a wheel of a passing vehicle, whereby the movable member is depressed by such wheel and the space is decreased by discharge of fluid thence to the low pressure source, and when the movable member nears the end of its downward movement, connecting the space with a source of high pressure fluid which acts, upon passage of the wheel vertically over the movable member, to urge the movable member upwardly with increased force, and finally reconnecting the space to the low pressure source substantially at completion of upward movement of the movable member.

10. A device for propelling a vehicle along a railway track, alongside which the device is located, comprising a cylinder having means to fix it uprightly to the track, a piston reciprocable in said cylinder and projecting upwardly for depression by a passing wheel, to effect inward movement of the piston into the cylinder and consequent lessening of the space enclosed between them, such space in use being filled with a liquid, a high pressure port and a low pressure port communicating with the enclosed volume of liquid at axially spaced points, a sleeve valve axially movable within the cylinder between an upper limit position wherein it affords communication between the low pressure port and the liquid-filled space, and a lower limit position wherein it alfords communication between the high pressure port and the liquid-filled space,

7 means to retain said sleeve valve yielclably in its limit positions, valve-operating means including a stem depending from the piston and engaging the sleeve valve as the piston approaches the limit of its outward movement, to shift the sleeve valve into its upper limit position, said valve-operating means further including a spring interposed between the sleeve valve and the piston, and ar- References Cited in the file of this patent UNITED STATES PATENTS Eccles Feb. 14, 1888 Checkley et a1 June 26, 1962 Bick Oct. 22, 1963 

1. A DEVICE FOR PROPELLING A VEHICLE ALONG A RAILWAY TRACK ALONGSIDE WHICH SAID DEVICE IS LOCATED, COMPRISING A UNIT HAVING RELATIVELY MOVABLE PISTON AND CYLINDER MEMBERS WHICH IN USE ENCLOSE A VOLUME OF LIQUID, ONE OF THE MEMBERS BEING ADAPTED FOR FIXED MOUNTING ADJACENT A TRACK RAIL AND THE OTHER MEMBER BEING ADAPTED FOR ENGAGEMENT BY THE PERIPHERY OF A VEHICLE WHEEL MOVING ALONG THE TRACK RAIL TO EFFECT RELATIVE INWARD CLOSING MOVEMENT OF SAID MEMBERS, VALVE MEANS COMMUNICATING WITH SAID VOLUME OF LIQUID AND HAVING HIGH AND LOW PRESSURE PORTS ARRANGED FOR CONNECTION WITH PRESSURE AND RETURN CONDUITS RESPECTIVELY OF A HYDRAULIC POWER SOURCE, SAID VALVE MEANS BEING OPERABLE TO CONNECT SAID ENCLOSED VOLUME OF LIQUID WITH THE HIGH AND LOW PRESSURE PORTS ALTERNATIVELY, AND VALVE-OPERATING MEANS RESPONSIVE TO THE DIRECTION OF RELATIVE MOVEMENT OF SAID MEMBERS, SAID VALVE-OPERATING MEANS BEING OPERATIVE TO CONNECT THE VALVE MEANS TO SAID VOLUME OF LIQUID WITH THE LOW PRESSURE PORT DURING RELATIVE INWARD CLOSING MOVEMENT OF SAID MEMBERS, AND WITH THE HIGH PRESSURE PORT DURING RELATIVE OUTWARD OPENING MOVEMENT OF SAID MEMBERS. 